examples: restore trace point

examples: restore trace point

Before make removal, those examples were built with experimental flag
for tracepoints to be compiled in but the pkg-config part of those
makefiles were missed.

Fixes: 78d44153de8f ("ethdev: add tracepoints")
Cc: stable@dpdk.org
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>